Cheese compositions are generally prepared from dairy liquids by processes that include treating the liquid with a coagulating or clotting agent. The coagulating agent may be a curding enzyme, an acid, a suitable bacterial culture, or an agent including a culture. The coagulum or curd that results generally incorporates casein that has been suitably altered by the curding process, fats including natural butter fat, and flavorings arising during the processing (especially when using a bacterial culture as the coagulating agent). The curd is usually separated from the whey. The resulting liquid whey generally contains soluble proteins not affected by the coagulation; such proteins are, of course, not incorporated into the coagulum because they are solubilized in the liquid whey.
Nevertheless, whey proteins have high nutritive value for humans. In fact, the amino acid composition in whey proteins is close to an ideal composition profile for human nutrition. Whey proteins are also understood to have superior emulsifying capabilities in comparison with casein. Without wishing to be bound by theory, this should reduce defects such as phase separation during processing, and, in the case of cream cheese, can also provide a smoother creamier product. In addition, such whey proteins provide a low cost dairy product which, if successfully incorporated into cheese products, would significantly increase the overall efficiency and effectiveness of the cheese-making process.
Cream cheese products are produced on large scale in the United States and ways to improve the product and to produce it in a more economical manner have been long sought in the dairy and food industry.
Unfortunately, methods or attempts to incorporate or use whey protein in cheese products have generally been unsuccessful. For example, whey proteins have been concentrated or dried from whey and then recombined with cheese (see, e.g., Kosikowski, Cheese and Fermented Foods, 2nd ed., Edwards Brothers, Inc., Ann Arbor, Mich., 1977, pp. 451-458). The whey proteins recovered from such procedures, however, do not have the appropriate or desired physical and chemical properties required for good, high quality natural cheeses or process cheeses.
Still other numerous attempts have tried various forms of modified native whey protein, modified, expensive whey protein isolate, or even cellular sources. For instance, a process for improving the functional properties of a protein-containing material selected from the group consisting of single-cell protein material, plant protein material, and mixtures of single-cell protein with plant material, whey solids or both plant protein and whey solids, in which the mixtures contain 1 to 99 weight percent of the single-cell protein is described in U.K. Patent 1,575,052. An aqueous slurry of the specified protein-containing material having 1 to 99 percent of the single cell protein is heated to a temperature of 75 to 100° C., the pH is adjusted to within the range of 6.6 to 8.0 by adding a compound selected from the group consisting of anhydrous ammonia, ammonium hydroxide, calcium hydroxide, sodium hydroxide, sodium bicarbonate, calcium sulfate, potassium carbonate, calcium carbonate, sodium carbonate, potassium hydroxide, magnesium hydroxide and mixtures thereof, maintaining the heated, pH-adjusted slurry under such conditions for 1 to 120 minutes, and then drying the material. The products are described as being capable of replacing nonfat dry milk in formulations which include bakery goods.
According to Watanabe et al., J. Dairy Res., 43:411 (1976), intermolecular disulfide bonds are formed when β-lactoglobulin is heated, with a maximum amount of such bonds being formed at pH 7.0. The β-lactoglobulin is the major protein component in whey and the covalent disulfide bonds link together individual proteins to form extended polymers. Larger sized aggregates are formed at 75° C. and smaller sized aggregates form at 97° C.
U.K. Patent Application 2,063,273A (Jun. 3, 1981) describes a method of preparing soluble denatured whey protein compositions that involves raising the pH of an aqueous solution of native whey protein to a pH of more than 6.5 and then heating the solution at a temperature and for a time greater than that at which the native whey protein is denatured and mentioned yogurt and salad dressing.
U.S. Pat. No. 5,416,196 to Kitabatake et al. describes a method of producing a transparent, purified milk whey protein having a salt concentration of less than 50 millimoles/liter. Using this purified whey protein in solution, Kitabatake et al. produced a whey protein product by adjusting the pH of the solution, readjusting the pH to either below 4 or above 6, and again heating the solution. This patent describes the use of whey protein from which the salts and saccharides normally contained in whey are substantially removed, for example by dialysis, chromatography, or microfiltration. While salt maybe re-added to the whey solution during processing for flavoring, this is done after adjusting the pH.
A heat treatment described in Hoffman, J. Dairy Res., 63:423-440 (1996) reportedly concerned formation of very large β-lactoglobulin aggregates at pH≦6.4.
Rheological properties and characterization of polymerized whey isolates are described in Vardhanabhuti et al., J. Agric. Food Chem., 47:3649-3655 (1999). The whey isolate was heat denatured and polymerized to produce soluble polymers. Whey isolate solutions in deionized water were prepared at concentrations of 8, 10, and 11 percent and heated in a water bath for 1, 3, and 9 hours at unspecified pH.
Gelation properties of polymerized whey protein isolates are described in Vardhanabhuti et al., Abstract 6-9, IFT Annual Meeting (1999). Whey polymers are described as being produced by heating a pH adjusted (pH 7.0) 11 percent protein solution of whey protein isolate (WPI) at selected salt concentrations of 10 mM CaCl2 and 200 mM NaCl.
U.S. Pat. No. 6,139,900 (Oct. 31, 2000) provides a complex, multi-heating step process for producing whey protein dispersions involving heating a 2 percent solution of whey protein isolate having a pH of at least 8.0 to 75° C. in a first heating step, cooling it, adjusting the pH to less than about 8.0 (e.g., 7.0), and heating the solution in a second heating step at a temperature of 75 to 97° C. to produce a polymerized whey protein product. This is a relatively complex, multi-step process that requires expensive starting materials and is relatively energy inefficient.
Whey protein isolate, which is required in the process of U.S. Pat. No. 6,139,900, is a highly purified and expensive product. Conventionally, whey protein isolate is made by drying and removing non-protein constituents from pasteurized whey so that the finished product contains more than 81 percent protein, typically greater than 90 percent, such as on the order of 98 percent protein. The highly purified whey protein isolate may contain small amounts of fat and lactose. Removing non-protein constituents can be achieved using physical separation techniques such as precipitation, filtration, or dialysis. The acidity of the final isolate product can be adjusted.
Whey protein concentrate (WPC) is more cost-effective than whey protein isolate (WPI) and can be easily produced on a much larger scale. It has a higher lactose but a lower protein content than whey protein isolate. It would be a significant advance in the art if WPC could be recovered from unit operations in an easy, reliably, economically, and energy efficient manner for use in the manufacture of dairy products, such as cream cheese type products.